Stereoselective domino conjugate addition of Grignard reagents to lactones followed by reaction with activated alkenes catalyzed by ferrocenyl carbene ligands

Asymmetric Transition-Metal Catalysis in the Formation and Functionalization of Metal Enolates

“…Stereoselective domino CA of Grignard reagents to lactone 81 followed by reaction with activated alkenes 82 was our next target (Scheme 25a). 80 Ferrocenylphosphane carbene ligand L16 was used to catalyze the CA. The target disubstituted lactones 83 were isolated in medium yields but with high enantiomeric and diastereomeric purities.…”

Trapping of chiral enolates generated by Lewis acid promoted conjugate addition of Grignard reagents to unreactive Michael acceptors by various electrophiles

“…3 A variety of substrates was utilized such as enones, esters, 4 thioesters, 5 and lactones. 6 A large variety of electrophilic reagents was used for enolate trapping. 7 We showed the trapping of Zr and Mg-enolates by carbocations.…”

Electrophilic Trapping of Zirconium Enolates Obtained by Copper-Catalyzed Addition of In Situ Generated Organozirconium Reagents

“…Tosylprotected imine 11 decomposed after its addition to the re-action mixture. Use of activated alkene 12, which Alexakis and our laboratory used in a similar processes with magnesium, zinc, and aluminum enolates, 49,50 provided the desired domino product rac-17a in 23% yield as a mixture of diastereoisomers (trans/cis = 3.7:1). Eschenmoser's salt 13 was insoluble in a reaction solvent; that is why no formation the corresponding domino product was observed.…”